Most fireworks or pyrotechnics launch projectiles or pyrotechnic effects from launch tubes that may include one-use disposable cardboard tubes. An aerial shell is an example of a pyrotechnic (fireworks) projectile, where the volume inside the shell is loaded with fireworks effects adjacent to or packed within a dispersive explosive, together referred to as a main burst. The pyrotechnic effects may include many different types of effects such as colored stars, hummers, whistles, etc. In conventional operation, upon detonation of the dispersive explosive, the pyrotechnic effects are dispersed and are subsequently ignited to give a typical visual pyrotechnic effect, such as one or more of colorful, sparkling, and/or streaming effects.
The projectiles come in many different shapes and sizes and shapes, but all are typically launched from a launcher (such a tube) with a lift charge which may be contained in an outer shell of the projectile and/or within the launch tube. For example, one suitable low-smoke producing launching system that may be used is found in U.S. Pat. No. 9,062,943, the disclosure of which is hereby incorporated by reference herein in its entirety.
Several factors contribute to the pyrotechnic projectile being successfully raised to a desired selected altitude within a selected time and with a subsequent successful main burst and dispersion of a pyrotechnic effect display. For example, the type and amount of lift charge used to propel the projectile, the size and weight of the projectile, the shape of the projectile, and the time delay of a fuse to ignite the main burst, are some of the many factors that may be desirably controlled.
For example, exemplary nitrocellulose and nitroguanidine based smokeless powders may be used within the lift charge (or within the dispersive charge enclosed within the aerial shell) are described in U.S. Pat. No. 9,217,624 “Spooling pyrotechnic device” which is hereby fully incorporated herein by reference.
Projectiles that include aerial shells containing fireworks effects have typically been constructed with a shell made from non-combustible materials or materials that cannot easily sustain combustion, such as paper, cardboard, molded plastic, glue, pressed wood particles, and tape.
In cases where the projectiles have included a fuse delay, the fuse delay has typically included chemical fuses such as columns of slow burning combustible material (self sustaining combustion) located below the main burst within a projectile or shell. In addition, a typical delay fuse may take the form of a chemical or electronic fuse that may penetrate the main burst from outside the aerial shell.
One problem with prior art chemical fuse systems has included the reliable lighting of the fuses upon launch and a sustainable burn rate of the fuses during flight.
One significant problem with prior art projectiles is projectile debris fallout upon explosion of the main burst. The projectile debris fallout may be undesirable in terms of obvious environmental and safety concerns. Some approaches in the prior art taken to address debris fallout have been to make the material of the projectile/shell destructible into a finer debris upon main burst explosion.
Another associated problem has been the requirement that the shell/projectile be formed of materials sufficiently strong to withstand resulting forces during and after launch and as well as the use of materials that may be produced without associated manufacturing non-uniformities that may degrade aerodynamic properties.
Therefore there is a continuing need in the art to provide a predictable and sustainably burning delay fuse associated with a pyrotechnics effects aerial shell that has improved aerodynamic properties and which upon main burst explosion produces little or substantially no debris.
It is therefore among the objects of the invention to provide a predictable and sustainably burning delay fuse associated with a pyrotechnics effects aerial shell that has improved aerodynamic properties and which upon main burst explosion produces little or substantially no debris.
These and other objects, aspects and features of the invention will be better understood from a detailed description of the preferred embodiments of the invention which are further described below in conjunction with the accompanying Figures.